Concentration of ores by flotation



g No Drawing.

Patented June 4, 1929.

. UNITED STATES PATENTYVIOFFICE.

ELMER KEISER BOLTON, OF WILMINGTON, DELAWARE, ASSIGNOR TO E. I. DO PON'I. DE. NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A. CORPORATION '01 DELAWARE.

containing a plurality of metalliferous minerals whereby improved selective concentra-' tion of the respective minerals is efiected.

It has been disclosed in my co-pending application of November 30, 1925, Serial No. 72147, that excellent results may be obtained in the recovery of ore values by flotation if .there is used in the flotation process a substance belonging to the class of compounds known as mercapto benzo thiazoles or the salts or oxidation products of such thiazoles.

It has now been found that such flotation reagents are unusually effective in the difl'erential and selective flotation of complex ores'or ores comprising various metalliferous minerals containing such element-sas lead, zinc, silver, copper, gold, etc. Exceptionally high recovery of minerals, accompanied by a high ratio of concentration can be obtained by the use of these reagents. Moreover, the amount of reagent required is small, as little as 0.02 pounds per ton of dry ore being sufiicient in many cases.

The effect of the mercapto benzo thiazole compounds is illustrated in the following examples which show the results obtained in the flotation of a typical lead-zinc ore from the Morning mine of the Federal Mining and smelting Company. This ore contains 7.8% lead and 5.9% zinc. The amounts of reagents employed are given in pounds per ton of dry ore. It is to be understood, of course, that these examples are purely illustrative and that it is not my intention to be limited to the particular conditions, procedure or reagents therein specified, which are all subject to variation to meet the needs of the particular case.

Example I.

" CONCENTRATION OF ORES BY FLOTATION.

Application filed May 22, 1926. Serial No. 111,052.

analyzed 45.5% lead and contained 82.7%

of the total lead. It also contained 25.7% of,

the total zinc. The ratio of lead to zinc was 4.2 to 1 indicating that mercapto benzo thi azole is a remarkably selective reagent.

For the purpose of comparison a similar test was made, using 0.10 pounds of potassium sults above.

' Pb Zn Pb-Zn ore 7.8% 5. 9% 1.3 to 1 Pb conc. (thiazole) 45. 5% 10.8% 4.2 to 1- Pb cone. (xanthate) 35. 4% 18.6% 1. 9 to 1 Example II. v

To illustrate the usefulness of the saltsof mercapto benzo thiazole, the fact thatzvery small quantities may be employed and that they are also very efiective in raising zinc-in a second period of flotation, the following tests were made.

The procedure outlined in the example above was employed for effecting a concentration of the lead with the exception that 0.03 pounds of the sodium salt of mercapto benzo thiazole was used instead of 0.10 pounds of mercapto benzo thiazole. A lead rougher con centrate was obtained which contained 43.3% lead and 9.5% zinc, corresponding respectively to recoveries of 80.0% of the lead and 23.2% of the zinc. The ratio of lead to zinc was 4.56 to 1.

Then 0.8 pound of added to the flotation cell, followed by 0.08 pound. of the sodium salt of mercapto benzo thiazole. Then 0.15. pound of steam distilled pine oil was added and .froth removed for 5 minutes. A zinc concentrate was obtained which contained 31.4% zinc and 7.1% lead,

copper sulphate was taining 40.1% lead and 11.9% of zinc, correspondmg to recoveries respectively of 80% of the lead and 31.7% of the zinc. The ratio of lead to zinc was only 3.4 to 1.

In the zinc-lifting period with the xanthate a concentrate was obtained which contained 28.1% zinc and 6.7% lead corresponding respectively to recoveries of 65.8% of the zinc and 11.9% of the lead.- The ratio of zinc to lead was 4.2 to 1.

The superior results obtained by using the sodium salt of mercapto benzo thiazole are compared below with those obtained with the xanthate salt.

Pb Zn as;

Pb-Zn oro 7. 8% 5.9% 1. 3 to 1 Pb cone. (thiazole) 43. 3% 9. 5% 4. 66 to 1 Pb cone. (xanthato) 4a 1% 11. 9% a. 4 to 1 Zn cone. (thiazole) 7. 1% 81. 4% 1 to 4. 42

Zn cone. (xanthato) a 7% 28. 1% 1 to 4. 2

It will be noted that in each of the examples the usual conditioning reagents, such as sodium sulphite, sodium cyanide and copper sulphate are employed. The general function and method of use of such reagents with known flotation agents is well known in the art. With mercapto-benzo-thiazole compounds, however, as witnessed above, extraordinary results are obtained. The cyanide, for instance, is used for depressing t e zinc sulphide during the lead raising step and the copper sulphate for cleaning or activating the zinc sulp ide prior to its flotation in the zinc raising step. A froth producing agent, as pine oil, hard wood creosote or terpineol is also normally employed. Also, although the pulp was not made alkaline in the embodiments illustrated an alkaline pulp will sometimes prove advantageous, depending upon the particular ore emplloyed, as is ,well understood in the art. he ores treated may, of course,'contain more than two minerals and the rocess of selection in such cases may be carried out by merely repeating the flotation step for each ore it is desired containing the following atomic grouping c-sn 1) 2 For example, recoveries of ore values, with high yields, have been obtained using as flotation agents such aromatic mercapto-thiazoles as mereapto-benzo-thiazole, 1-mercapto-3- methyl-benzo-thiazole, and mercapto-alpha naphthLthiazole. And instead of a mercapto-thiazole, a salt thereof may be used, asl'for example the sodium salt, or the zinc sa t.

The manner of preparation of the mercapto benzo thiazoles for use in the process is no part of my invention. They may be prepared in any suitable manner, for example, in a manner similar to that described by Sebrell and Boord in their article on the preparation and properties of lv-mprcapto-benzo-thiazole, its homologues and derivatives, published in vol. 45, on page 2390-015 the Journal of the American Chemical Society.

It will be obvious from the foregoing embodiments and description of my invention that the class of compounds, the properties of which I have discovered, constitutes unusually selective and eflicient flotation reagents. These compounds are adapted for use over a wide range of conditions for the differential or selective flotation of complex ores. I believe myself to be the first to discover these valuable properties and claim as my invention:

1. In the process .of difl'erentially concentrating minerals by flotation, the step which comprises subjecting a complex sulphide ore in the form of a pulp to a froth flotation operation in the presence of a metal salt of 1- mercapto benzo thiazole, said flotation operation being selective with respect to the different sulphides.

2. In the process of differentially concentrating minerals by flotation, the step which comprises subjecting a complex sulphide ore in the form of a pulp to a froth flotation operation in the presence of the sodium salt of l-mercapto benzo thiazole, said flotation operation being selective with respect to the different sulphides.

3. In the process of differentially concentrating minerals by flotation, the step which comprises subjecting a complex ore in the form of a pulp to a froth flotation operation in the presence of a metal salt of the group consisting of the sodium and zinc salts of l-mercapto benzo thiazole, said flotation operation being selective with respect to the different ores.

4. The improvement in the selective concentration of minerals by flotation which comprises subjecting an ore containing a plurality of minerals and to which has been added a mercapto benzo thiazole compound to a flotation operation adapted to yield a froth relatively rich in one of said minerals, removing said froth, adding a mercapto benzo thiazole to the ore and then subjecting it to a second flotation operation adapted to yield a froth relatively rich in another of said minerals.

5. The improvement in the selective concentration of minerals: by flotation which comprises subjecting a complex ore in the form of a pulp to a flotation operation in the presence of a mercapto thiazole compound, a frothing agent and a conditioning agent adapted to promote the formation of a mineral-bearing froth relatively rich in one mineral, separating said froth and further agitating the remaining pulp after the addition of further quantities of a mercapto thiazole compound, frothing agent and a condition ing agent adapted to promote the formation of a second froth relatively rich'in another mineral and removing said second froth.

6. The improvement in the selective concentration of minerals by flotation which comprises subjecting an ore in the form of a pulp containing galena and sphalerite to a flotation operation in the presence of a mercapto thiazole compound, a frothing agent and a conditioning agent adapted to depress the sphalerite and produce a mineral-bearing froth relatively rich in galena, separating said froth and further agitating the remaining pulp after the addition of a conditioning agent adapted to facilitate the flotation of the sphalerite, a mercapto thiazole compound and a frothing agent and separating a second froth relatively rich in sphalerite.

7. The improvement in the selective concentration of minerals by flotation which comprises subjecting an ore in the form of.

pulp containing galena and sphalerite to a flotation operation in the presence of v l-mercapto benzo "thiazole, sodium cyanide and a frothing agent to form a mineral-bearing froth relatively rich in galena, separating said froth and again agitating the remaining pulp after the addition of further quantities of l-mercapto benzo thiazole, together with a mineral frothing agent and copper sulphate and separating a second froth relatively rich in sphalerite.

8. The improvement in the concentration of minerals by flotation which comprises subjecting the ore in the form of pulp containing galena and sphalerite to a selective flotation operation adapted to form in the presence of a sodium salt of l-mercapto benzo thiazole and a mineral frothing agent a mineralbearing froth relatively rich in galena, separating said froth and again subjecting the remaining pulp after the addition of further quantities of the sodium salt of l-lnercapto benzo thiazole and a frothing agent to a flotation operation adapted to separate a second froth relatively rich in sphalerite.

9. The improvement in the concentration of minerals by flotation which comprises subjecting the ore in the form of pulp containing galena and sphalerite to a selective flotation operation adapted to form, in the presence of a compound of the group consisting ofvthe sodium and zinc salts of l-mercapto benzo thiazole and a mineral frothing agent, a mineral-bearing froth relatively rich in galena, separating said froth and again subjecting the remaining pulp, after the addition of further quantities of said salt of l-mercapto benzo thiazole and a frothing'agent to a flotation operation adapted to separate a second froth relatively rich in sphalerite.

10. The process of treating an ore containing a plurality of metalliferous minerals which comprises agitating an aqueous pulp of said ore in the presence of a mercapto benzo thiazole compound, a frothing agent, and a conditioning agent adapted to depress at least one but not all of said minerals, and removing the resulting froth.

11. The process-of treating an ore containing a plurality of metalliferous minerals which comprises agitating an aqueous pulp of said ore in the presence of a mercapto benzo thiazole compound, a frothing agent, and a conditioning agent adapted to depress at least one but not all of said minerals, removing the resulting froth, adding further quantities of a mercapto benzo thiazole compound, a frothing agent and a second conditioning agent adapted, together with said frothing agent, to form a froth relatively rich in one of the minerals depressed in the first operation.

In testimony whereof I affix my signature.

ELMER K. BOLTON. 

